Mosquito season in Iroquois County, IL: when it starts and ends
Mosquito months in Iroquois County
In a normal year mosquito season in Iroquois County, IL starts around April 14 and ends around October 24, about 28 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Iroquois County, and when
- Start tipping out standing water weekly by March 31.
- Book any yard treatment for mid April, ahead of the July peak.
- Repellent can go away after October 24.
- No West Nile cases since 2016, so bites in Iroquois County are a nuisance; check window screens.
Iroquois County against the rest of IL
Iroquois County has the 76th longest season of 102 IL counties, at 193 days against 232 in Pulaski County and 174 in Boone County. Its mean temperature is 50.9°F.
- McDonough County: April 13 to October 23 (193 days, 1 WNV)
- Rock Island County: April 13 to October 23 (193 days, 3 WNV)
- Woodford County: April 15 to October 25 (193 days, 3 WNV)
- Warren County: April 13 to October 22 (192 days, 1 WNV)
West Nile in Iroquois County
From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Iroquois County (0 neuroinvasive) across 1 year. The worst was 2015 with 1; the latest was 2015.
More: how the dates are worked out · when mosquitoes go away for the winter.